Most of the jars I see these days have a plastic strip and a foil seal hot/ultrasonically welded to the top of the jar. Personally, I would just wash out the tops with soap and water. The foil/plastic seal should keep contamination out of the food. Of course, most of the jars I've seen with the seal are the unbreakable plastic jars but I doubt I would have a problem with the glass jars. The plastic that you must peel off around the glass jar lids seem to be capable of keeping contaminates out from under the lids. ^_^
TDD